//#pragma comment(linker,"/STACK:16777216") /*16Mb*/
//#pragma comment(linker,"/STACK:33554432") /*32Mb*/
#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<numeric>
#include<sstream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<memory>
#include<string>
#include<vector>
#include<cctype>
#include<list>
#include<queue>
#include<deque>
#include<stack>
#include<map>
#include<set>
#include<algorithm>
using namespace std;

typedef unsigned long long      ui64;
typedef long long               i64;
typedef	vector<int>             VI;
typedef	vector<bool>            VB;
typedef	vector<VI>              VVI;
typedef	vector<string>          VS;
typedef	pair<int,int>           PII;
typedef map<string,int>         MSI;
typedef set<int>                SI;
typedef set<string>             SS;
typedef map<int,int>            MII;
typedef	pair<double,double>     PDD;

#define PB                      push_back
#define MP                      make_pair
#define X                       first
#define Y                       second
#define FOR(i, a, b)            for(int i = (a); i < (b); ++i)
#define RFOR(i, a, b)           for(int i = (a) - 1; i >= (b); --i)
#define CLEAR(a, b)             memset(a, b, sizeof(a))
#define SZ(a)                   int((a).size())
#define ALL(a)                  (a).begin(), (a).end()
#define RALL(a)                 (a).rbegin(), (a).rend()
#define INF                     (2000000000)

bool letter( char c ) {
	return ( (c>='a' && c<='z') || (c>='A' && c<='Z') || c==' ' );
}

int main()
{
	int n,m;
	cin >> n >> m;
	/* m >= n*/
	string s;
	getline(cin,s);
	getline(cin,s);
	VI dp(SZ(s),0);
	int last = -1;
	//dp[0]=0;
	FOR(i,0,SZ(s)) {
		if( !letter(s[i]) ) {
			last = i;
		}
		
		if( i<n ) {
			dp[i] = 1;
			continue;
		}

		if( last!=i ) {
			if( last==-1 ) {
				if( i>=m )
					dp[i] = dp[i-m]+1;
				else
					dp[i] = 1;
			}
			else
				dp[i] = min(dp[i-n],dp[max(last,i-m)])+1;

			continue;
		}
		dp[i] = dp[i-n] + 1;
	}
	cout << dp[SZ(s)-1] << endl;
	/*Why not greedy?*/
    return 0;
}